Project-based learning units are often used for large scale work integrated learning (WIL) experiences in Liberal Studies Degrees as they offer scalability and sustainability of delivery to large cohorts. This systematic search and review evaluates the effectiveness of interdisciplinary project-based learning in Science Degree programs for developing discipline knowledge and employability skills. Education literature databases were searched for peer-reviewed journal articles that discussed undergraduate science-based degree programs with project-based learning units involving students from multiple disciplines. Data were analysed for evidence of a skill gain in 6 areas (Discipline knowledge, Communication, Teamwork, Interdisciplinary effectiveness, Critical thinking and problem solving, and Self-management). Projects were assigned to categories based on interdisciplinary breadth and depth. Data was analysed by cross-tabulations, Fisher’s Exact test and by calculating odds ratios (OR), which indicate the effect size. Perception of a skill gain was significantly more likely to be reported than an objectively measured skill gain (p<0.001). Real discipline skill gains were 6.6 times more likely in projects narrow in discipline mix (OR 6.6), however perceived discipline skill gains were high irrespective of project type. Projects with wide interdisciplinarity were significantly associated with perceived gains in interdisciplinary effectiveness (OR 32, p<0.05) and more likely to have perceived gains in communication (OR 2.5) and teamwork (OR 3.4) skills. When projects have greater interdisciplinary breadth or depth, perceived student employability skill gains increase, perceived discipline skill gains are unaffected, however actual discipline skill gains are less reported. Further research and evidence that project-based learning is meeting the desired WIL learning objectives of the curriculum is needed.